1. Field of the Invention
The present invention generally relates to satellite position location systems and, more particularly, to a method and apparatus for location-based triggering in an assisted satellite positioning system (SPS).
2. Description of the Background Art
Location-based triggering refers to instances where the geographical position of a mobile device triggers a predetermined event. For example, an event may be triggered when a mobile device enters or leaves a predefined area. The event may be local to the mobile device (e.g., an alarm), or may be linked to a network with which the mobile device communicates (e.g., a change in billing rates in a cellular telephone network). One practical application of location-based triggering technology is “home zone billing”. More specifically, home zone billing is a feature that may enable a cellular phone service to compete with landline telephone service providers by charging customers reduced rates when they use their cellular phone, in lieu of their traditional telephone, while they are at home (i.e., the predefined area or zone).
One implementation of location-based triggering requires a network to continuously monitor a predefined area in order to determine if the mobile device remains at home throughout the duration of a call. The geographical position may be determined using a position location system, such as a satellite position location system (e.g., the Global Positioning System (GPS)). Although this method can be readily implemented, it requires the network to frequently update the position of the user. Such continuous updating, however, results in frequent and excessive use of valuable network resources.
Another implementation of location-based triggering that is aimed toward restricting the number of communications between the network and the mobile device utilizes a cell-site identifier (“cell ID”) as the basis for a positioning method. The mobile device monitors the ID of the serving cell-site (e.g., base station) and triggers an event when a change in the serving cell is detected. Such a technique, however, lacks the desired accuracy and precision required for some applications (e.g., home zone billing). Furthermore, such a technique may also encounter problems pertaining to boundary conditions in situations where the predefined area includes the boundaries of several cell-sites.
Therefore, there is a need in the art for a method and apparatus that can perform location-based triggering with greater accuracy and reliability.